Ecotoxicological testing with new kinetic Photorhabdus luminescens growth and luminescence inhibition assays in microtitration scale

Miniaturized luminescence and growth inhibition assays in microtitration pl ates with the terrestric enthomopathogenic nematode symbiont Photorhabdus l uminescens (DSMZ 3368T) are presented and compared with standardized tests with Vibrio fischeri (DSMZ 7151/NRRLB-11177) and Pseudomonas putida (DSMZ 5 0026). Toxicological parameters (EC and G values) of selected reference tox icants (e.g. heavy metals and environmental samples) were obtained at diffe rent temperatures and without sodium chloride supplementation Kinetic data recordings were compared with results of a cuvette test protocol using inte gral and endpoint calculation. Growth inhibition experiments with reference samples reveal similar or higher sensitivities as for the Vibrio or Pseudo monas spp. The luminescence inhibition assay shows reduced sensitivities to most of the reference samples compared with the V. fischeri standard assay . But G values obtained with other standardized aquatic assay systems with daphnids, algae and growth inhibition assays with V. fischeri and Ps. putid a correspond more closely to data observed with Ph. luminescens. The test p rocedures are easily to perform and to evaluate and seem to be reliable alt ernatives to the established protocols at low osmolarities. The sample spec ifity of the toxic responses of the marine and the terrestric strain recomm ends to employ both assays to determine the toxic potential of environmenta l samples. This will support to reduce false positive results in future inv estigations. (C)1998 Elsevier Science Ltd. All rights reserved.